MATTHEW DALY Associated Press Published: October 26, 2012 4:36 AM

From athletes and astronauts to singers and Hollywood stars, a growing line of celebrities is turning up at fancy dinners and rallies to build support and get out the vote for Obama or Romney, the president's Republican challenger.

Obama has entertainers like Bruce Springsteen, Katy Perry, George Clooney, Beyonce and Jay-Z.

Both campaigns have spent huge amounts of time and effort making sure their rallies feature opening acts that reinforce a campaign message, whether it's the economy, health care, veterans or some other issue.

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Nicklaus, who now designs golf courses, teed up Romney at a campaign event near Columbus, Ohio.

The golfer said he's had to lay off workers because of the struggling economy. "We can't keep doing what we've been doing. We have to look at the problems at hand and change them," he said.

On the Democratic side, Pearl Jam frontman Eddie Vedder ripped into Romney at an Obama fundraiser in Florida. Vedder said he was upset by Romney's caught-on-tape comments that 47 percent of Americans consider themselves victims and entitled to government help. If Romney wins the White House, "none of those 47 percent of people would have a voice," Vedder said.

Aaron, who wore No. 44 for the Milwaukee and Atlanta Braves, urged a crowd in Wisconsin to re-elect Obama, president No. 44. Appearing with Obama in Milwaukee, Aaron said one of the most touching moments of his life was when Obama was elected as the country's first black president.

"As one who wore the number 44 on his back for decades, I ask you to join me in helping the 44th president of the United States hit a grand slam," said Aaron, the last Negro League player to compete on a major league roster.

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After retired space-shuttle astronaut Sid Gutierrez trumpeted Republican vice presidential candidate Paul Ryan in Florida last month, Obama countered with his own famous former astronaut. Former Ohio Sen. John Glenn, the first American to orbit the earth, appeared with a rally with the president.

Singer Will.i.am, who wrote the song "Yes We Can" for Obama's 2008 run, also was on stage that day. Obama joked that the singer "sometimes looks like he's been to outer space," while Glenn "has actually been to outer space."

Celebrity warm-up acts may draw news coverage, but they're unlikely to have a lasting effect on the election, said Darrell West, director of governance studies at the Brookings Institution think tank.

Even so, appearances by high-profile supporters can validate candidates "by taking them out of the political realm into popular culture," West said.

"Voters are cynical about candidates and think they will say anything to win," West said. "Having a nonpolitical opening act gives politicians credibility at a time of massive cynicism."